Method of self-servo writing in a disk drive using multiple timing windows

ABSTRACT

A disk drive includes a head and a disk, spiral patterns are located on the disk, and the disk drive self-writes servo patterns on the disk using the spiral patterns as a reference for servoing the head. In an embodiment, the disk drive uses preliminary servo patterns to determine repeatable runout of the spiral patterns. In another embodiment, the disk drive reads each spiral pattern with multiple timing windows.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 10/128,959filed on Apr. 23, 2002 now U.S. Pat. No. 7,088,533.

FIELD OF THE INVENTION

The present invention relates to disk drives, and more particularly todisk drive self-servo writing.

BACKGROUND OF THE INVENTION

In many processing and computing systems, magnetic data storage devicessuch as disk drives are used for storing data. A typical disk driveincludes a spindle motor for rotating one or more data storage diskshaving data storage surfaces, a head arm that supports one or moretransducer heads, and an actuator for moving the heads radially acrossthe disks to enable the heads to read from and write to concentrictracks on the disks.

In general, the head is positioned very close to the corresponding disksurface. Typical clearance between the head and a smooth disk surface isabout one microinch, or less. The close proximity of the head to thedisk allows recording very high density servo patterns (embedded servoinformation) and user data on the disk.

The servo patterns are typically written into servo sectors with uniformcircumferential (angular) spacing, and data sectors or blocks areinterleaved between the servo sectors. The servo patterns are alsoarranged in radially extending servo spokes that are interspersed atregular intervals between user data areas on the disk. In addition, theservo patterns are radially close enough to allow servoing at anarbitrary radial position. At a given radius, the servo patterns includecoarse identifiers and fine identifiers. The coarse identifiers provideradius and timing information when the head presents a read signal withsufficient amplitude to detect digital data. The fine identifiers arecircumferentially sequential, radially staggered, single frequencybursts that provide radial position information when the head is offsetfrom a track centerline enough to present a read signal with partialamplitude.

The servo patterns provide the disk drive with head position informationto control the actuator to move the head from starting tracks todestination tracks during random access track seeking operations.Further, the servo patterns provide the disk drive with head positioninformation to control the actuator to position and maintain the head inproper alignment with a track during track following operations whenuser data is read from or written to data sectors in concentric trackson the disk surface.

In a standard manufacturing process, a head-disk assembly (HDA) of thedisk drive is assembled in a clean room and then transported to aspecialized servo writer where the HDA is mounted on a stabilizedmetrological measurement system. Then, in a time consuming process, theservo writer uses the head to write the servo patterns to the disk. Thedrive electronics are then assembled to the HDA and the disk drive ismoved to a self-scan station where the disk drive is tested for reliableservo operation. Block errors, defects, control tracks and otherinformation are written to the disks at this station. If the disk drivefails the self-scan tests, it is either reworked or scrapped at thislate manufacturing stage.

Servo writers write the servo patterns with various processes. Forexample, a skip-track process writes the servo patterns at every otherradius and then writes intermediate servo bursts at every skippedradius. As another example, a sync-skip process writes reference servopatterns at every other radius and then writes final servo patterns atevery radius. The sync-skip process avoids the time-consuming step ofmeasuring and compensating for head reader-to-writer offsets.

Disk drives have been developed that self-servo write the servo patternswithout a servo writer. For example, an incremental two-pass self-servowrite process begins with a first pass that writes reference servopatterns at a position determined by a crash-stop (the mechanical limitof the head's movement) and then servos on the reference servo patternsand writes the next set of reference servo patterns. The first passrepeats as the head moves radially across the disk, with each stepservoing on the previously written reference servo patterns to write thenext reference servo patterns at the next radial position. During thefirst pass, the servo loop has no absolute reference to ensure placementof the reference servo patterns at the appropriate radius. After thefirst pass finishes the complete stroke, a second pass writes the finalservo patterns using the reference servo patterns to find theappropriate positions. However, the second pass substantially increasesthe self-servo writing time.

There is, therefore, a need for improved disk drive self-servo writingwhich reduces servo writer time, reduces self-servo writing time,improves performance and is simple to implement.

SUMMARY OF THE INVENTION

The present invention satisfies these needs. The present inventionprovides a disk drive with a head and a disk, spiral patterns arelocated on the disk, and the disk drive self-writes servo patterns onthe disk using the spiral patterns as a reference for servoing the head.

In an embodiment, the disk drive writes the servo patterns using thespiral patterns and preliminary servo patterns as a reference forservoing the head. For example, the preliminary servo patterns are usedto determine repeatable runout of the spiral patterns, and the diskdrive writes the servo patterns using the spiral patterns and therepeatable runout for servoing the head.

In another embodiment, the disk drive reads each spiral pattern withmultiple timing windows to provide multiple signal amplitudes of a readsignal and uses the signal amplitudes for servoing the head. Forexample, a first timing window is aligned with a first space-delimitedburst at a rising edge of the read signal to provide a first averagesignal amplitude, a second timing window is aligned with a secondspace-delimited burst at a falling edge of the read signal to provide asecond average signal amplitude, and the signal amplitudes are used forservoing the head.

BRIEF DESCRIPTION OF DRAWINGS

These and other features, aspects and advantages of the presentinvention will become understood with reference to the followingdescription, appended claims and accompanying figures where:

FIG. 1 shows a diagrammatic view of a printing station for printing areference pattern on a reference disk;

FIG. 2A shows a diagrammatic view of a disk drive including thereference disk, several blank disks and drive electronics for self-servowriting using the reference pattern in a self-scan station;

FIG. 2B shows a simplified diagram the disk drive and a computer andincludes details the drive electronics;

FIG. 2C shows a simplified diagram of a channel chip in the driveelectronics;

FIG. 3 shows spiral patterns of the reference pattern on the referencedisk;

FIG. 4A shows the spiral patterns, preliminary servo patterns and servospokes on the reference disk;

FIG. 4B shows servo tracks and data tracks on the reference disk;

FIG. 5 shows a first position detection method;

FIG. 6 shows a second position detection method;

FIG. 7 shows a third position detection method;

FIGS. 8A-8B show a self-servo writing process using the referencepattern and the preliminary servo patterns; and

FIGS. 9A-9B show another self-servo writing process using the referencepattern and the preliminary servo patterns.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1 shows a printing station 10 that writes a reference pattern 12 toa disk surface 14 of a magnetic reference disk 16.

FIG. 2A shows the reference disk 16 and other disks 18 assembled on aspindle 20 of a disk drive 22 being assembled. The spindle 20 is mountedwithin a head-disk assembly (HDA) 24 and is rotated at a predeterminedangular velocity by a spindle motor 26. A comb-like actuator assembly 28is included in the HDA 24. The actuator assembly 28 includes head arms30 rotated by a voice coil motor (VCM) 32 to position the transducerheads 34 and 36 adjacent to the disk surface 14 of the reference disk 16and to the disk surfaces 38 of the disks 16 and 18. The disk surface 14is the top surface of the reference disk 16, and the disk surfaces 38are the bottom surface of the reference disk 16 and the top and bottomsurfaces of the disks 18. The disk surface 14 includes the referencepattern 12 and the disk surfaces 38 are blank at this stage. Thus, thedisks 18 are blank at this stage. After the disks 16 and 18 and theheads 34 and 36 are installed, the HDA 24 is enclosed by a cover toprevent unwanted particulate contamination. The drive electronics 40,such as a printed circuit board (PCB) carrying large scale integratedcircuits and other components, is mechanically attached to the HDA 24and is electrically connected to the HDA 24 by a suitableinterconnection 42 to complete the mechanical assembly of the disk drive22. The disk drive 22 is then placed in a self-scan station 44 andconnected to a suitable power supply, and a control and statuscollection computer (not shown) collects data about the disk drive 22during self-scan procedures.

The drive electronics 40 controls the head 34 to read the referencepattern 12 from the reference disk 16, and in turn enables the heads 34and 36 to write final servo patterns in circular and concentric servotracks on the disks 16 and 18. The final servo patterns are used by aservo loop in the drive electronics 40 to position the heads 34 and 36over target tracks on the disks 16 and 18 to record and playback userdata.

FIG. 2B shows the disk drive 22 connected to a computer 25 via a bus 23.The disk drive 22 includes a preamplifier 19 for amplifying read signalsprovided by the heads 34 and 36. The drive electronics 40 includes amicroprocessor 15 for servo loop control of the disk drive 22, acontroller 17 (including a control processor 27) primarily forcontrolling data flow communications with the computer 25 via the bus 23and also for controlling components of the disk drive 22, and a channelchip 21 for processing data transferred between the microprocessor 15,the controller 17, the preamplifier 19 and the computer 25.Alternatively, the microprocessor 15 can be a component of thecontroller 17. The microprocessor 15 can include an integrated circuitprocessor chip which performs floating point arithmetic, integermathematics, transforms, etc. The computer 25 can include the statuscollection computer.

FIG. 2C shows a simplified version of the channel chip 21. The channelchip 21 includes a sampling digital detector 29 coupled to thepreamplifier 19 for digitally sampling the read signals from the heads34 and 36 in response to reading from the disks 16 and 18. A signalprocessor 31 receives digital samples from the sampling digital detector29 and processes the digital samples to extract position informationembedded in the amplitude and phase of the read signals. The channelchip 21 provides the measurements of the signal processor 31 to themicroprocessor 15 for head position detection, servoing, headpositioning and servo writing.

The present invention includes (1) the reference pattern 12 instead ofcoarsely-spaced servo patterns from conventional skip-track andsync-skip processes which require more time, and (2) the disk drive 22positioning the heads 34 and 36 using the reference pattern 12 as thedisk drive 22 self-servo writes the final servo patterns to concentricand circular servo tracks on the disks 16 and 38.

FIG. 3 shows the reference pattern 12 on the reference disk 16. Thereference pattern 12 is composed of spiral patterns 50. The spiralpatterns 50 are each an essentially continuous high frequency pattern ofbursts that extends from an inner diameter (ID) to an outer diameter(OD) of the reference disk 16. The spiral patterns 50 can all be read ata constant radius during a single revolution of the reference disk 16.

FIG. 4A shows a linear view of the spiral patterns 50, the preliminaryservo patterns 52 and the servo spokes 54 on the reference disk 16. Thepreliminary servo patterns 52 are located at the OD of the referencedisk 16, although alternatively, they can be located at the ID of thereference disk 16. The preliminary servo patterns 52 are also located incircular and concentric servo tracks on the reference disk 16. The servospokes 54 extend radially from the preliminary servo patterns 52 towardsthe ID of the reference disk 16 and traverse most of the radial distancebetween the ID and OD of the reference disk 16. The servo spokes 54 alsooverwrite the spiral patterns 50 where they intersect. Furthermore, theservo spokes 54 include final servo patterns that are located incircular and concentric servo tracks on the reference disk 16.

The reference pattern 12 and the preliminary servo patterns 52 can beprovided on the reference disk 16 using the printing station 10 beforethe reference disk 16 is installed in the HDA 24, as discussed above.Alternatively, the reference pattern 12 and the preliminary servopatterns 52 can be provided on the reference disk 16 using the head 34and a servo writer after the reference disk 16 is installed in the HDA24. For example, the spiral patterns 50 are written sequentially andcontinuously except for a minimal gap or interruption between thebursts. Each spiral pattern 50 is written by the head 34 as the head 34moves from the OD to the ID (or the ID to the OD) of the reference disk16 at a constant clock and pitch while the reference disk 16 spins 10 to50 revolutions. The pitch is the angle between the spiral pattern 50 anda circular track, that is, the slew velocity (radius versus disk angle)that the spiral pattern 50 is written at, with the radius measured inLPS counts, tracks or micro-inches, and the disk angle measured inradians, degrees, clock ticks, or spokes.

The disk drive 22 uses the preliminary servo patterns 52 to spin-up tooperating speed, acquire servo lock, and read disk-ware.

The disk drive 22 also uses the preliminary servo patterns 52 tocharacterize the spiral patterns 50. The characteristic can be a timingcharacteristic between the spiral patterns 50 and the preliminary servopatterns 52. For example, the disk drive 22 locks onto the preliminaryservo patterns 52 and characterizes the repeatable runout (RRO) of thespiral patterns 50. The RRO can be due to eccentricity of the spiralpatterns 50 relative to the center of the reference disk 16. The spiralpatterns 50 each have a starting point between a pair of the preliminaryservo patterns 52, at which point the RRO characterization begins. Sincethe preliminary servo patterns 52 are radially located at the OD of thereference disk 16, the preliminary servo patterns 52 characterize theRRO of the spiral patterns 50 at the OD of the reference disk 16. Anindividual spiral pattern 50 has nearly the same RRO fromtrack-to-track. Thus, the RRO is measured/characterized once for thespiral pattern 50 at the OD of the reference disk 16, and oncecharacterized, is similar from one track to the next.

The disk drive 22 uses the spiral patterns 50 and the characterized RROduring a self-scan process to servo the head 34 for self-servo writingthe servo spokes 54. The disk drive 22 locks onto to the spiral patterns50 using a position detection method, as described below. The disk drive22 then slews to the starting point just past the preliminary servopatterns 52, writes final servo patterns in the servo spokes 54, seeksto the next half-track, writes the next pass of final servo patterns inthe servo spoke 54, and so on. As a result, the servo spokes 54overwrite portions of the spiral patterns 50. Moreover, the RRO in thespiral patterns 50 is accounted for in determining the relative positionof the head 34 as the spiral patterns 50 rotate under the head 34.Residual adjustment can be accumulated across many tracks while theself-servo writing proceeds.

Since the spiral patterns 50 have portions overwritten by the servospokes 54, the spiral patterns 50 generally outnumber the servo spokes54. For example, the number of the spiral patterns 50 is about 250,which is twice or more the number of the servo spokes 54.

The spiral patterns 50 are of primary significance for self-servowriting the servo spokes 54, and the preliminary servo patterns 52enhance self-servo writing the servo spokes 54. Furthermore, the spiralpatterns 50 and the preliminary servo patterns 52 provide a referencefor self-servo writing the servo spokes 54.

The disk drive 22 uses the servo spokes 54 a servo loop in the driveelectronics 40 to position the heads 34 and 36 over data tracks on thedisks 16 and 18 to record and playback user data on the disks 16 and 18.

FIG. 4B shows servo tracks 60 and data tracks 62 on the reference disk16. Although disk surface 14 is shown, it is representative of the otherdisk surfaces 38. The servo tracks 60 and the data tracks 62 arecircular and concentric tracks. The servo tracks 60 are formed by theservo spokes 54 and include servo sectors that contain the final servopatterns. Thus, the disk drive 22 self-writes the servo tracks 60 as theservo spokes 54 and vice-versa. The final servo patterns include aseries of phase-coherent digital fields followed by a series of constantfrequency servo bursts. The servo bursts are circumferentiallysequential, radially staggered, and provided in sufficient number thatfractional amplitudes of the read signal generated by the head 34 inresponse to portions of one or more of the servo bursts passing underthe head 34 enable the disk drive 22 to determine and maintain theproper position of the head 34 relative to each data track 62. The datatracks 62 include individually addressable data sectors 64 in which userdata is stored. The data sectors 64 are separated by the embedded servosectors in the servo spokes 54.

After the disk drive 22 self-servo writes the servo spokes 54 (and thusthe servo tracks 60), the disk drive 22 can write the data tracks 62 atany radial position relative to the servo tracks 60. For example, fiveservo tracks 60 designated as Sa, Sb, Sc, Sd and Se are shown inrelation to three data tracks 62 designated as Tk1, Tk2 and Tk3. Theservo tracks 60 each include radially similarly situated servoinformation in the servo spokes 54. For example, the servo track Secontains servo information at essentially same radial distance from thecenter of the reference disk 16, the servo track Sd contains servoinformation at essentially same radial distance from the center of thereference disk 16, etc.

The disk drive 22 locks onto to the spiral patterns 50 to self-write theservo spokes 54 using a position detection method that relies oncoherence of the bursts in the spiral patterns 50. If the referencepattern 12 is written using a servo writer, the bursts in each spiralpattern 50 are clocked by the servo writer to ensure coherence.

During the self-servo writing, as the reference disk 16 rotates and thehead 34 is stationary, the head 34 generates a read signal in responseto each spiral pattern 50 that it reads from the reference disk 16. Theread signal has a signal envelope with a football-like shape thatincludes leading and trailing edges. The disk drive 22 determines theposition of the head 34 by measuring the amplitudes of the leading andtrailing edges using successive timing windows. For example, a firsttiming window measures the leading edge and a second timing windowmeasures the trailing edge.

The timing of the timing windows is fixed to the rotation of thereference disk 16. As the head 34 moves towards the ID or the OD of thereference disk 16, for instance due to RRO in the spiral pattern 50, thetiming windows stay open while the signal envelope moves according tothe spiral pattern 50 pitch and off-track error. The disk drive 22 usesthe timing windows to measure the amount of signal envelope movement andtranslate it into the position of the head 34 relative to the spiralpatterns 50.

Furthermore, the timing for the timing windows is derived from a clockthat coasts from one spiral pattern 50 to another. A spiral pattern 50rotates under the head 34 to provide a read signal that is sampled bythe timing windows, and the read signal is used to determine when toopen the timing windows for the next spiral pattern 50. Thus, theself-servo writing clock propagates from one spiral pattern 50 toanother.

FIGS. 5, 6 and 7 show first, second and third position detectionmethods, respectively. The circumferential (down-track) direction ishorizontal, and the radial (cross-track) direction is vertical. A reader66 of the head 34 follows a circular track on the reference disk 16along a circumferential path 70 that has a centerline 72 and boundaries74. The spiral pattern 50 is skewed relative to the path 70 at a pitchangle 76. As the reader 66 crosses the spiral pattern 50, the reader 66generates a read signal in response to the spiral pattern 50. The readsignal has a signal envelope with a football-like shape that includesleading (rising) and trailing (falling) edges when viewed on anoscilloscope. The read signal increases and then decreases in proportionto the amount of overlap between the reader 66 and the spiral pattern50. The reader 66 may be narrower than the spiral pattern 50, in whichcase the read signal has a flat section at its maximum point when thereader 66 is within the spiral pattern 50. The read signal is sampledduring successive timing windows shown by the upper square waves. Thesignal amplitudes of the read signal that are sampled and measuredduring the timing windows are then used to position the head 34 as thehead 34 writes a servo spoke 54 during the self-servo writing. Then, asthe reader 66 crosses the next spiral pattern 50, the next read signalis sampled during the timing windows and the signal amplitudes are usedto position the head 34 as the head 34 writes the next servo spoke 54during the self-servo writing. The process repeats as the head 34 readsthe next spiral pattern 50 and then writes the next servo spoke 54.

FIG. 5 shows the first position detection method. The path 70 crossesover an area 78 of the spiral pattern 50. The read signal is sampledduring the timing windows 80 and 82, once by the timing window 80 duringthe leading or rising edge A, and again by the timing window 82 duringthe trailing or falling edge C.

The timing window 80 is nominally aligned with the leading edge, beginsbefore the leading edge, ends during the leading edge, includesessentially the entire leading edge and excludes the trailing edge. Thetiming window 82 is nominally aligned with the trailing edge, beginsduring the trailing edge, ends after the trailing edge, includesessentially the entire trailing edge and excludes the leading edge.

If the timing T of the timing windows 80 and 82 is not changed, anyradial variation in the path 70 relative to the spiral pattern 50 willcause a corresponding variation in the signal amplitudes of the A and Cmeasurements. The difference in the signal amplitudes of the A and Cmeasurements indicates the radial position of the head 34 relative tothe spiral pattern 50. The head 34 is at the correct radial positionwhen the difference is zero.

A target position of the head 34 defines the desired timing T of thetiming windows 80 and 82 (T_(A) for timing window 80 with measurement A)as:T _(A)(target)=T _(A0) +K ₁(target position−reference position)

where the multiplier K₁ is proportional to the slew-rate at which thespiral pattern 50 (reference position) is written (microseconds/track).

The position error between the target position and the actual positionof the head 34 is obtained by:position error=K ₂(amplitude(C)−amplitude(A))

where the multiplier K₂ is proportional to the width and sensitivity ofthe reader 66 (tracks/full-scale amplitude).

The read signal measurement is analogous to that of traditional servobursts and can be accomplished with the same traditional hardware.

The spiral patterns 50 have no gaps except where the servo spokes 54 arewritten, and the timing windows 80 and 82 separate the signal envelopeinto two halves (A and C). The disk drive 22 attempts to equalize theintegrated signal on either side of the signal envelope split to keepthe head 34 in a circular track as the servo spokes 54 are written.

FIG. 6 shows the second position detection method. The path 70 crossesover an area 84 of the spiral pattern 50. The area 84 includes highfrequency bursts separated by an information field 86. The read signalis sampled during the timing windows 80, 82 and 88, once by the timingwindow 80 at the burst during the leading edge A, again by the timingwindow 88 at the information field 86 during the intermediate or flatedge B, and again by the timing window 82 at the burst during thetrailing edge C.

The timing window 80 is nominally aligned with the leading edge, beginsand ends during and is within the leading edge and excludes the flat andtrailing edges. The timing window 88 is between the timing windows 80and 82, is nominally aligned with the flat edge and excludes the leadingand trailing edges. The timing window 82 is nominally aligned with thetrailing edge, begins and ends during and is within the trailing edgeand excludes the flat and leading edges.

The position of the head 34 is determined in the same manner as thefirst position detection method. In addition, the information field 86provides a gap between the leading and trailing bursts to prevent smallvariations in the timing of the timing windows 80 and 82 from affectingthe signal amplitudes of the A and C measurements because the edges ofthe timing windows 80 and 82 enter the information field 86 but do notextend across the information field 86 to the burst on the oppositeside.

The information field 86 includes digital information, similar that oftraditional servo patterns, such as a track number, ordinal spiralpattern number, automatic gain control pattern, timing pattern,synchronization pattern and/or gray code.

FIG. 7 shows the third position detection method. The spiral pattern 50is a series of high frequency bursts 90 (A, B, C) that have amplitudes92, include high frequency patterns 94 and are separated by gaps 96. Theread signal is sampled during the timing windows 98, with each burst 90is sampled by a corresponding timing window 98. The timing windows 98are nominally aligned with cover the bursts 90.

The signal amplitude profile is comparable to that of the secondposition detection method. Furthermore, arbitrary position variationscan be handled by reading enough of the bursts 90. Although theamplitude 92 of each burst 90 is not constant across the length of theburst 90, this is inconsequential because the measurement of the burst90 represents the simple integration (or average value) of the burst 90.

The position of the head 34 is determined in the same manner as thefirst position detection method. In addition, the gaps 96 between thebursts 90 prevent small variations in the timing of the timing windows98 from affecting the signal amplitudes of the A and C measurementsbecause the edges of the timing windows 98 enter the gaps 96 but do notextend across the gaps 96 to the bursts 90 on the opposite side.

In this example, there are two bursts 90 per track and the gaps 96 areabout ten percent of the bursts 90. Because the writer of the head 34 issmaller than a track width, the crossover points in the amplitudes 92are less than fifty percent. This is similar to an untrimmed two-passper track servo pattern. Alternatively, there can be three bursts 90 forevery two tracks, which is similar to an untrimmed 3/2 servo pattern.

Since the bursts 90 are written on the same pass (during a singlerevolution of the reference disk 16) and the bursts in the servo spokes54 are written on different passes (during multiple revolutions of thereference disk 16), the bursts 90 have similar off-track properties yetless noise than trimmed bursts in the servo spokes 54.

The first, second and third position detection methods have varioustradeoffs. The first position detection method is relatively simple(compared to the other two) but the accuracy depends on precise timingof the timing windows. The track profile is linear only during the flatsof the signal envelope, and the flat length depends on the head 34reader-to-writer width ratio. In addition, the first position detectionmethod detects movement across essentially the entire leading andtrailing edges, whereas the second position detection method detectsmovement only over the width of the first and second timing windows. Thesecond position detection method provides more robust timing accuracythan the first position detection method and is linear over a widerrange than the first position detection method but does not have as higha signal level as the first position detection method. The thirdposition detection method also provides more robust timing accuracy thanthe first position detection method. In addition, the third positiondetection method provides position information at any track location,whereas the first and second position detection methods provide positioninformation primarily in the vicinity of specific track locations (thetarget position).

FIGS. 8A-8B show a self-servo writing process that includes writing thespiral patterns 50 and the preliminary servo patterns 52 on thereference disk 16 using a servo writer, then assembling the HDA 24 tothe drive electronics 40, then characterizing the timing of the spiralpatterns 50, and then servoing on the spiral patterns 50 using thecharacterized timing for self-writing the servo spokes 54. The processincludes the following steps:

1. Assemble the HDA 24 (step 100);

2. Place the HDA 24 on the servo writer (step 101);

3. Spin up the HDA 24 (step 102);

4. Move the heads 34 and 36 to the crash-stop and reset the positioningsystem (step 103);

5. Write a clock track on one of the disks 16 and 38 using a clock head(step 104);

6. While moving the heads 34 and 36 in a spiral, coordinated with theclock track, write a spiral pattern 50 between the radial limits (ID andOD) of the reference disk 16, starting at a defined circumferentialposition at one radial limit, and repeat writing the spiral patterns 50starting at other equally-spaced circumferential positions to create thereference pattern 12 (step 105);

7. Write the preliminary servo patterns 52 for one revolution of thereference disk 16, and optionally, repeat writing the preliminary servopatterns 52 starting at each radial position over a range to create aband of the preliminary servo patterns 52 (step 106);

8. Spin down the HDA 24 (step 107);

9. Remove the HDA 24 from the servo writer, and mate the HDA 24 to thedrive electronics 40 (step 108);

10. Perform a self-scan post-servo writer process, including:

11. Spin up the HDA 24 (step 109);

12. Move the heads 34 and 36 to the crash-stop (step 110);

13. Find the preliminary servo patterns 52 (step 111);

14. Read the preliminary servo patterns 52 and characterize timing withrespect to the spiral patterns 50 (step 112). The preliminary servopatterns 52 include unique information defining their position, whichcan be read by the head 34 during a single pass over the preliminaryservo patterns 52. For example, the head 34 may read “track 50001,sector 7” from a preliminary servo pattern 52. In contrast, the positioninformation available from the spiral patterns 50 may not be unique. Forexample, the head 34 may only be able to read “01” from a spiral pattern50. In order to determine absolute position, it is convenient to read apreliminary servo pattern 52, then switch to a spiral pattern 50 at thesame location, and keep track of changes in position and time from onespiral pattern 50 to the next;

15. Switch from servoing on the preliminary servo patterns 52 toservoing on the spiral patterns 50, and write concentric final servopatterns in the servo spokes 54 for one revolution of the reference disk16 based on the characterized timing (step 113). In order to smoothlysplice into the reference pattern 12, it is useful to characterize thefine-grained irregularities in the reference pattern 12. Theirregularities may come from thermal or mechanical shifts in positionbecause the spiral patterns 50 were written by the servo writer. This isparticularly useful for bulk-writing in which the reference disk 16 isplaced in the disk drive 22 after the spiral patterns 50 have beenwritten by the printing station 10. If the reference disk 16 isinstalled in the HDA 24 slightly off-center, the spiral patterns 50 mayhave substantial systematic position error in the disk drive 22,however, the characterized timing accounts for such errors.Alternatively, steps 112 and 113 can be combined into a simpler step,after step 111, of reading the preliminary servo patterns 52 toestablish an initial reference position for the spiral patterns 50;

16. Continue to servo on the spiral patterns 50 and write a next set ofconcentric final servo patterns in the servo spokes 54 at apredetermined radial spacing (track-to-track) from the previouslywritten final servo patterns (step 114); and

17. Repeat step 114 for each radial position from the OD to the ID ofthe reference disk 16 until all the final servo patterns are written(for instance, until the crash-stop limit is reached) (step 115).

FIGS. 9A-9B show another self-servo writing process that includeswriting a few spiral patterns 50 on the reference disk 16 using a servowriter, then assembling the HDA 24 to the drive electronics 40, thenwriting the preliminary servo patterns 52 on the reference disk 16, thencharacterizing the timing of the spiral patterns 50, then servoing onthe spiral patterns 50 using the characterized timing to position thehead 34 to begin self-writing the servo spokes 54, and then servoing onthe previously written final servo patterns in the servo spokes 54 tocontinue self-writing the servo spokes 54. The process includes thefollowing steps:

1. Assemble the HDA 24 (step 200);

2. Place the HDA 24 on the servo writer (step 201);

3. Spin up the HDA 24 (step 202);

4. Move the heads 34 and 36 to the crash-stop and reset the positioningsystem (step 203);

5. Write a clock track on one of the disks 16 and 38 using a clock head(step 204);

6. While moving the heads 34 and 36 in a spiral, coordinated with theclock track, write a spiral pattern 50 between the radial limits of thereference disk 16, starting at a defined circumferential position at oneradial limit (step 205);

7. Optionally repeat step 205 writing more spiral patterns 50 startingat different circumferential positions (step 206);

8. Spin down the HDA 24 (step 207);

9. Remove the HDA 24 from the servo writer and mate the HDA 24 to thedrive electronics 40 (step 208);

10. Perform a self-scan post-servo writer process, including:

11. Spin up the HDA 24 (step 209);

12. Move the heads 34 and 36 to the crash-stop (step 210);

13. Write the preliminary servo patterns 52 for one revolution of thereference disk 16 (step 211);

14. Read the preliminary servo patterns 52 and characterize timing withrespect to the spiral patterns 50 (step 212);

15. Switch from servoing on the preliminary servo patterns 52 toservoing on the spiral patterns 50 and write concentric final servopatterns in servo spokes 54 for one revolution of the reference disk 16using the characterized timing (step 213);

16. Switch from servoing on the spiral patterns 50 to servoing on thepreviously written final servo patterns and write a next set ofconcentric final servo patterns in the servo spokes 54 at apredetermined radial spacing from the previously written final servopatterns (step 214); and

17. Repeat step 214 for each radial position from OD to the ID of thereference disk 16 until all the final servo patterns are written (step215).

The self-servo writing can be implemented as firmware in the driveelectronics 40 by configuring the microprocessor 15, the controller 17and/or the channel chip 21 to functionally provide a position detectorand a control loop. The self-servo writing can also be implemented inother ways such as ASIC or software.

A quantitative example of the self-servo writing is as follows:

RPM=6000

TPI=25,000 (tracks per inch)

full stroke=1 inch (TPI=tracks per full stroke)

clock speed=100 MHz

servo spokes=125

bursts per track=2

Tcell per burst=1000bits per revolution=clock speed/(RPM/60)=100,000,000/(6000/60)=1,000,000

To determine the pitch angle 78 for writing the spiral patterns 50, thefollowing relation is used:revolutions per spiral pattern (revolutions per full-stroke)=tracks perfull stroke)/(bits per revolution/((bits per burst)(bursts pertrack)))=25,000/(1,000,000/(1000×2))=50

50 revolutions per spiral pattern=4 tracks per spoke

The self-servo writing time is as follows:(125 servo spokes)(2 spiral patterns per servo spoke)(50 revolutions perspiral pattern)/(100 revolutions per second)=125 seconds

The present invention has been described in considerable detail withreference to certain preferred versions thereof; however, other versionsare possible. Therefore, the spirit and scope of the appended claimsshould not be limited to the description of the preferred versionscontained herein. In particular, the present invention may beimplemented equivalently in hardware, software, firmware, and/or otheravailable functional components or building blocks.

1. A method of self-servo writing in a disk drive, wherein the diskdrive includes a head and a disk, and the disk includes a spiralpattern, the method comprising: reading the spiral pattern from the diskusing the head to generate a read signal; measuring a first averagesignal amplitude of the read signal during a first timing window at aleading edge of the read signal; measuring a second average signalamplitude of the read signal during a second timing window at a trailingedge of the read signal; and writing a final servo pattern on the diskusing the head and using the signal amplitudes to position the head. 2.The method of claim 1, wherein the read signal has a signal envelopewith a football-like shape.
 3. The method of claim 1, wherein the firsttiming window begins before the leading edge, and the second timingwindow ends after the trailing edge.
 4. The method of claim 1, whereinthe first timing window is within the leading edge, and the secondtiming window is within the trailing edge.
 5. The method of claim 1,wherein the first timing window excludes the trailing edge, and thesecond timing window excludes the leading edge.
 6. The method of claim1, wherein spiral pattern includes first and second space-delimitedbursts, the first timing window is aligned with the firstspace-delimited burst and the second timing window is aligned with thesecond space-delimited burst.
 7. The method of claim 6, includingwriting the space-delimited bursts to the disk using the head during asingle revolution of the disk.
 8. The method of claim 1, including:reading a previous spiral pattern from the disk using the head togenerate a previous read signal; and opening the timing windows based onthe previous read signal.
 9. The method of claim 1, including obtaininginformation in the read signal based on the spiral pattern during athird timing window between the first and second timing windows, andwriting the final servo pattern without using the information toposition the head.
 10. The method of claim 9, wherein the informationincludes at least one of a track number, a spiral pattern number, anautomatic gain control pattern, a timing pattern, a synchronizationpattern and a gray code.
 11. A method of self-servo writing in a diskdrive, wherein the disk drive includes a head and a disk, and the diskincludes a spiral pattern, the method comprising: reading the spiralpattern from the disk using the head to generate a read signal, whereinthe read signal has a signal envelope with a football-like shape;measuring a first average signal amplitude of the read signal during afirst timing window at a leading edge of the read signal and outside atrailing edge of the read signal; measuring a second average signalamplitude of the read signal during a second timing window at thetrailing edge and outside the leading edge; and writing a final servopattern on the disk using the head and using the signal amplitudes toposition the head.
 12. The method of claim 11, wherein the first timingwindow begins before the leading edge, and the second timing window endsafter the trailing edge.
 13. The method of claim 11, wherein the firsttiming window is within the leading edge, and the second timing windowis within the trailing edge.
 14. The method of claim 11, wherein theread signal does not have a constant amplitude during the first timingwindow, and the read signal does not have a constant amplitude duringthe second timing window.
 15. The method of claim 11, wherein the readsignal has an increasing amplitude during the first timing window, andthe read signal has a decreasing amplitude during the second timingwindow.
 16. The method of claim 11, wherein spiral pattern includesfirst and second space-delimited bursts, the first timing window isaligned with the first space-delimited burst and the second timingwindow is aligned with the second space-delimited burst.
 17. The methodof claim 16, including writing the space-delimited bursts to the diskusing the head during a single revolution of the disk.
 18. The method ofclaim 11, including: reading a previous spiral pattern from the diskusing the head to generate a previous read signal; and opening thetiming windows based on the previous read signal.
 19. The method ofclaim 11, including obtaining information in the read signal based onthe spiral pattern during a third timing window between the first andsecond timing windows, and writing the final servo pattern without usingthe information to position the head.
 20. The method of claim 19,wherein the information includes at least one of a track number, aspiral pattern number, an automatic gain control pattern, a timingpattern, a synchronization pattern and a gray code.
 21. A method ofself-servo writing in a disk drive, wherein the disk drive includes ahead and a disk, and the disk includes a spiral pattern, the methodcomprising: reading the spiral pattern from the disk using the head togenerate a read signal; measuring a first average signal amplitude ofthe read signal during a first timing window that is nominally alignedwith a leading edge of the read signal; measuring a second averagesignal amplitude of the read signal during a second timing window thatis nominally aligned with a trailing edge of the read signal; andwriting a final servo pattern on the disk using the head and using thesignal amplitudes to position the head.
 22. The method of claim 21,wherein the read signal has a signal envelope with a football-likeshape.
 23. The method of claim 21, wherein the first timing windowbegins before the leading edge, and the second timing window ends afterthe trailing edge.
 24. The method of claim 21, wherein the first timingwindow is within the leading edge, and the second timing window iswithin the trailing edge.
 25. The method of claim 21, wherein the firsttiming window excludes the trailing edge, and the second timing windowexcludes the leading edge.
 26. The method of claim 21, wherein spiralpattern includes first and second space-delimited bursts, the firsttiming window is aligned with the first space-delimited burst and thesecond timing window is aligned with the second space-delimited burst.27. The method of claim 26, including writing the space-delimited burststo the disk using the head during a single revolution of the disk. 28.The method of claim 21, including: reading a previous spiral patternfrom the disk using the head to generate a previous read signal; andopening the timing windows based on the previous read signal.
 29. Themethod of claim 21, including obtaining information in the read signalbased on the spiral pattern during a third timing window between thefirst and second timing windows, and writing the final servo patternwithout using the information to position the head.
 30. The method ofclaim 29, wherein the information includes at least one of a tracknumber, a spiral pattern number, an automatic gain control pattern, atiming pattern, a synchronization pattern and a gray code.
 31. A methodof self-servo writing in a disk drive, wherein the disk drive includes ahead and a disk, the disk includes a spiral pattern, and the spiralpattern includes space-delimited bursts, the method comprising: readingthe spiral pattern from the disk using the head to generate a readsignal; measuring average signal amplitudes of the read signal duringtiming windows that are nominally aligned with the space-delimitedbursts; and writing a final servo pattern on the disk using the head andusing the signal amplitudes to position the head.
 32. The method ofclaim 31, wherein the read signal has a signal envelope with afootball-like shape.
 33. The method of claim 31, wherein the read signaldoes not have a constant amplitude during any of the timing windows. 34.The method of claim 31, wherein the read signal has an increasingamplitude during one of the timing windows, and the read signal has adecreasing amplitude during another of the timing windows.
 35. Themethod of claim 31, wherein the timing windows have identical duration.36. The method of claim 31, wherein the timing windows cover thespace-delimited bursts.
 37. The method of claim 31, including writingthe space-delimited bursts to the disk using the head during a singlerevolution of the disk.
 38. The method of claim 31, including: reading aprevious spiral pattern from the disk using the head to generate aprevious read signal; and opening the timing windows based on theprevious read signal.
 39. The method of claim 31, including obtaininginformation in the read signal based on the spiral pattern duringanother timing window between the timing windows, and writing the finalservo pattern without using the information to position the head. 40.The method of claim 39, wherein the information includes at least one ofa track number, a spiral pattern number, an automatic gain controlpattern, a timing pattern, a synchronization pattern and a gray code.41. A method of self-servo writing in a disk drive, wherein the diskdrive includes a head and a disk, the disk includes a spiral pattern,and the spiral pattern includes first and second space-delimited bursts,the method comprising: reading the spiral pattern from the disk usingthe head to generate a read signal; measuring a first average signalamplitude of the read signal during a first timing window that isnominally aligned with the first space-delimited burst at a leading edgeof the read signal; measuring a second average signal amplitude of theread signal during a second timing window that is nominally aligned withthe second space-delimited burst at a trailing edge of the read signal;and writing a final servo pattern on the disk using the head and usingthe signal amplitudes to position the head.
 42. The method of claim 41,wherein the read signal has a signal envelope with a football-likeshape.
 43. The method of claim 41, wherein the read signal does not havea constant amplitude during the first timing window, and the read signaldoes not have a constant amplitude during the second timing window. 44.The method of claim 41, wherein the read signal has an increasingamplitude during the first timing window, and the read signal has adecreasing amplitude during the second timing window.
 45. The method ofclaim 41, wherein the timing windows have identical duration.
 46. Themethod of claim 41, wherein the first timing window covers the firstspace-delimited burst and the second timing window covers the secondspace-delimited burst.
 47. The method of claim 41, including writing thespace-delimited bursts to the disk using the head during a singlerevolution of the disk.
 48. The method of claim 41, including: reading aprevious spiral pattern from the disk using the head to generate aprevious read signal; and opening the timing windows based on theprevious read signal.
 49. The method of claim 41, including obtaininginformation in the read signal based on the spiral pattern during athird timing window between the first and second timing windows, andwriting the final servo pattern without using the information toposition the head.
 50. The method of claim 49, wherein the informationincludes at least one of a track number, a spiral pattern number, anautomatic gain control pattern, a timing pattern, a synchronizationpattern and a gray code.